How do I make all these faces lay flat ? without changing the scale?
First create a plane that you would like to align them all to. 

Second If they are not already individual objects, go into edit mode and hit P to separate by loose parts. 

Then enable snapping by clicking the magnet button and set up the settings as you see here:



Finally, select the parts in object mode hit G to move them. Put your cursor on the plane, then they should rotate to match the plane.